In a multi-system including two or more systems, a relay can be used for controlling transmission of data or signals between the systems. In particular, when isolation between the systems is required, an isolated switch such as a photo MOS relay is used.
In the multi-system using the photo MOS relay in the related art, in the case where transmission of data or signals from a primary system to a secondary system is controlled, in general, when an LED of the photo MOS relay is in an ON state, a contact of a load of the secondary system is connected and when an event such as an emergency situation occurs and the contact of the load thus needs to be cut, the LED becomes in an OFF state and the contact of the load is configured to be cut.
As described above, in the system in the related art in which the LED included in the isolated switch is in an emission state at normal times and the LED is turned off when the event occurs, a duration for which the LED is maintained in the emission state is long, and as a result, power consumed for emitting the LED is wasted and a life-span of the isolated switch including the LED is shortened, and as a result, durability of the system adopting the isolated switch deteriorates.
Therefore, in the system in the related art, which includes the isolated switch, it is preferable to decrease the duration for which the LED is maintained in the emission state.
In particular, in an energy storage system using a secondary battery, a system having a stop function in an emergency situation requires designing a structure to maintain the LED of the isolated switch in the off state at normal times and control the LED in the on state in the emergency situation.